Metal is utilized as an important constituent of a catalyst for chemical reaction. Even in the case of being limited to the field of organic synthesis, catalysts including metal, particularly transition metal, are applied to various types of reactions, such as reduction reaction, oxidation reaction, hydrometalation, carbon-carbon bond forming reaction, and carbon-nitrogen bond forming reaction, and are reagents indispensable for production of a large amount of industrial products, pharmaceutical products, or agricultural chemicals.
Meanwhile, transition metal includes many rare elements, such as platinum and palladium, which are classified into rare metal and are often expensive because the reserves and the production volume are limited. Accordingly, from the perspective of costs and effective use of resources, there is a demand for recycling transition metal. For further efficiency, there is also a strong request for recovering and reusing a transition metal catalyst.
As a technique for recovering and reusing or continuously using a transition metal catalyst, a transition metal catalyst has been immobilized on a polymer or an inorganic material.
For example, a report describes that, reduction reaction that is hydrogenation of the carbon-carbon double bond proceeds using a catalyst having rhodium as transition metal supported by polystyrene having phosphine as a substituent group that can coordinate to rhodium (NPL 1).
In another example, olefin metathesis reaction proceeds using a catalyst including ruthenium supported by polyethylene glycol having carbene or phosphine as a substituent group that can coordinate to ruthenium, and a polyethylene glycol supported catalyst is recovered by adding diethyl ether as a poor solvent (NPL 2).
In the case of using palladium, allylation reaction is carried out by being supported by polystyrene to successfully recover the catalyst (PTL 1).